Flying into the sky is not only a human dream but also a very efficient mode of transportation. It possesses the efficiency of quickly arriving at the destination. Therefore, it can remove the gap between people caused by space. Consequently, flying is not only with entertainment and business nature, but also with a further great demand for other applications.
For a fixed-wing aircraft, it is true that it can carry a large number of personnel and goods, but such a vehicle needs a long runway and a lot of related takeoff and landing equipment, thus only confined to the airport takeoff and landing. To overcome this restriction, a rotorcraft, such as a helicopter, which is capable of vertical takeoff and landing, is additionally developed. But even if for a rotorcraft capable of vertical takeoff and landing, a considerable area of apron still needs to be set up and it is unable to pickup and drop off passengers like a ground vehicle. Moreover, it is still difficult for a helicopter to enter a narrow passageway and an ordinary roof in the metropolis with high-density buildings.
Therefore, there have currently been research and development teams starting to research and develop single vertical lift aircrafts available to be used in the metropolis with high-density buildings and narrow space. Some of currently known single vertical lift aircrafts use a single propeller, while a plurality of propellers, generally with double propeller, four propeller and other different types, can be disposed to get bigger thrust. However, the volume of a single vertical lift aircraft is quite limited. If a plurality of propellers are disposed, it is inevitably impossible to be like a fixed-wing aircraft to equip each propeller with an individual engine. Instead, it is hoped to use an engine to simultaneously drive a plurality of propellers. Therefore, it is an important issue how to distribute and transmit the power of an engine to each propeller.